A method of manufacturing chopped strands in which after glass filaments allowed to flow out of nozzles provided on the bottom of a spinning furnace are coated with coating agent, the glass filaments are collected in the form of a strand, and the glass filaments are allowed to stick onto the surface of a feed roller to be stretched to be fibrous, and then the glass filaments are cut into pieces of a predetermined length by means of a cutter roller abutted against of the feed roller to provide chopped strands, is well known in the art, for instance, by Japanese Patent Publication No. 27089/1975. In this prior art, after glass filaments allowed to flow out of the nozzles provided on the bottom of a spinning furnace are coated with coating agent, the glass filaments are collected in the form of a strand and are allowed to contact the outer surface of a feed roller over its predetermined angle so that the glass filaments are stretched to be fibrous with the aid of a frictional adhesion force due to the contact. In addition, under the condition that the glass filaments in the form of a strand have a contact angle at which the frictional adhesion force is greater than the stretching force, the glass filaments in the form of a strand are cut into pieces of a predetermined length by a cutter roller abutted against the feed roller to thereby provide glass fiber chopped strands.
In the above-described Japanese Patent Publication, with rotation of the cutter roller, the feed roller is rotated at the same circumferential speed so as to conduct both the stretching operation for making the molten glass fibrous and the supplying operation of the strand to the engagement section between the cutter roller and the feed roller possible. Therefore, it is necessary that the strand sticks completely onto the surface of the feed roller with the aid of the frictional force.
Furthermore, there are a great variety of filament diameters, filament numbers, cut lengths, coating agent concentrations, and coating agents. For instance, for filament diameter, the following equation can be established between fibrous degree (A) of glass fiber filament and a fiber forming circumferential speed (B): EQU a=f (B1/2)
accordingly, in the case where it is requested to provide a filament of 10.mu. diameter under the conditions of the filament fibrous degree 13.mu. and the fiber forming speed 1200 m/min, for example, the manufacture is carried out by keeping other spinning conditions constant and increasing the circumferential velocity of the feed roller to 2000 m/min. In this case, as the circumferential speed of the fiber forming feed roller is equal to that of the cutter roller, the velocity of the cutter roller is also increased. As a result, the dropping direction of chopped strand is determined by a relation between the adhesion force of a chopped strand to the cutter roller, the centrifugal force thereof and the adhesion force thereof to the surface of the feed roller. Increase of the cutting speed results in increase of the adhesion force of the chopped strand toward the cutter roller, that is, the adhesion force of the strand is relatively decreased, and therefore the dropping direction is changed toward the side of the feed roller. In contrast, if the cutting speed is decreased, the dropping direction is changed toward the side of the cutter roller. In addition, according to the variations in the number of filaments, the cutting length, the coating agent concentration and the kind of the coating agent, the adhesion force to the feed roller is varied. Furthermore, as the strand which is wound on and delivered by the surface of the feed roller has been coated with coating agent and is still wet, an excessive coating agent is removed from the strand gradually by a winding tension applied to the strand on the feed roller, and thus the apparent adhesion force of the strand is increased with time. Accordingly, the dropping direction of chopped strand tends to deflect toward the feed roller.
As for the displacement with coating agents, if the viscosity thereof is relatively low, the displacement is effected toward the cutting roller side and if relatively high, the displacement is effected toward the feed roller side.
In the case where a cutter roller having a diameter d and cutting edges A-A embedded therein forming an angle Q with respect to the axis is employed as is shown in FIG. 2 when the strand is moved in the axial direction of a feed roller by means of a traverse device, the cutting position of the cutter roller is changed with respect to the feed roller, as a result of which the dropping direction of chopped strand is also changed.
It is now assumed that the dropping direction of a strand chopped by the middle point a of the cutter roller is as indicated by reference character (a). Since the cutting edge is straight and skewed with respect to the cutting roller, a locus drawn by the tip of each cutting edge of the cutter roller which the latter rotates increases in diameter as it goes to both ends. Therefore, if the cutting point is moved to b from a, the dropping direction is changed from (a) to (b); and if the cutting point is further moved from b to c, then the dropping direction is changed from (b) to (c). In contrast, if the cutting point is moved to b' and then to c', the dropping direction is changed to (b') and then to (c').
Accordingly, whenever the strand being wound on the feed roller is moved in the axial direction, the chopped strand dropping direction is changed. Therefore, cutting of the strand must be carried out by controlling the dropping direction at all times, otherwise, the accumulation of the chopped strands will be onesided as shown in FIG. 1a or FIG. 1b.
These drawbacks may be overcome by accumulating the chopped strands at a position where the variation in accumulation state of the chopped strands is small, that is, if the distances between the cutting points and the accumulation position are made small. However, in case where a strand is wet with the coating agent and then cut into pieces, if the chopped strands are accumulated at a position near the cutting point, the chopped strands, being struck against the accumulation are scattered, as a result of which the strands are broken and become fluffy, that is, the quality of the strands becomes worse. Accordingly, in the case of the cutting speed of for example, from 1000 to 1500 m/min., the distance between the cutting point and the accumulation area should be more than 1000 mm. As the chopped strand contains water which is 10-20% in weight and coated with a coating agent, the weight of which is 0.16 to 1.5%, with respect to the total weight of the strand, water and the agent respectively, it has been found that it is necessary to dry and cure the chopped strands. However, the accumulation state of the chopped strands piled on the accumulation area affects the drying efficiency thereof greatly. If a usual hot-air dryer is employed to dry the chopped strands and if the chopped strands are piled to form an uneven accumulation, the drying conditions of the chopped strands accumulated on the accumulation area are varied. The chopped strands forming a convexed accumulation, for example, may not be completely dried, while the chopped strands forming a concaved accumulation include excessive amounts of coating agent which may change the hardness of the strands or color the strands. In the case where a high-frequency induction heating type drying system is employed, the absorption of energy is proportional to the strand accumulation configuration. Especially for the concaved accumulation, the absorption energy is approximately zero, and therefore some of the strands will not be dried.
In this view point, too, the uniform delivery of the chopped strand onto the accumulation area is highly desired.